The present invention relates to a deformation structure and to a pedestrian protection device having a deformation structure which is arranged between a body outer skin element and a body carrier element.
A known front end of a motor vehicle has, for example, a bumper cross member which is fastened to front ends of longitudinal members, and a bumper cladding, wherein a soft foam which is deformable at a comparatively low load level is arranged between the bumper cladding and the bumper cross member in order to protect pedestrians. On account of pedestrian protection, the soft foam is arranged in order to protect a pedestrian where appropriate against direct and immediate collision with a hard, stiff structure of the motor vehicle, such as, for example, the bumper cross member.
Furthermore, it is required for the motor vehicle to remain free from damage in a collision in a very low speed range of up to, for example, 4 km/h, in which the pedestrian protection is irrelevant because of the low speed.
Furthermore, at a somewhat higher speed, which is likewise still not relevant for pedestrian protection, it is required that damage during a collision is as small as possible and, for example, a radiator structure which is located in the front end region is not damaged. For this purpose, it would be helpful if the structure which is located in front of the bumper cross member already has adequate capability of absorbing collision energy.
The different requirements are partially in conflict with one another and require a comparatively long vehicle overhang at the vehicle front and therefore a higher weight, and are a disadvantageous influence on the driving dynamics.
In order to solve the resulting conflict of objectives, a bumper arrangement with a cross member which is fastened to the vehicle body via crash boxes has been proposed, for example, in DE 102010054641 A1. A pedestrian protection element for a soft impact against a pedestrian is formed in front of the cross member in the direction of travel. In addition, a pivotable energy absorption element is provided which is pivotable in front of the pedestrian protection element and thereby permits increased energy absorption in collisions in which a higher collision energy absorption capability of the crash structure of the motor vehicle is required.
DE 102012112636 A1 likewise shows a bumper arrangement, comprising a bumper cross member and a pedestrian protection element which can be switched over by means of an actuator from a stiff state into a comparatively soft state which serves for pedestrian protection.
A common feature of the bumper arrangements described in DE 102010054641 A1 and DE 102012112636 A1 is that a crash or pre-crash sensor system is required for this purpose wherein, on the basis of the output signals of the sensor system, a switch can be made between a hard, stiff state of the crash structure with high collision energy absorption capability and a soft state of the crash structure with low collision energy absorption capability in favor of pedestrian protection.
It is therefore the object of the present invention to provide a deformation structure and a pedestrian protection device having the deformation structure for a motor vehicle, said deformation structure being deformable at different energy levels depending on a load situation, and being of simple construction and functioning independently of a sensor system or an actuator.
This and other object are achieved by a deformation structure according to the invention, which may also be called an energy absorption structure, having at least one first layer and a second layer, which are arranged spaced apart from each other in the deformation direction or load direction and so as to be displaceable with respect to each other. The first layer and the second layer have complementary protrusions and depressions, which are designed in such a manner that the protrusions of the first layer and the depressions of the second layer and also the protrusions of the second layer and depressions of the first layer are insertable into one another. The first layer and the second layer are connected to each other via deformable web elements in such a manner that, in the event of a high impulse in the deformation direction, the protrusions of the first layer enter into the depressions of the second layer and also the protrusions of the second layer enter into the depressions of the first layer, and therefore deformation of the deformation structure in the deformation direction takes place at a relatively low force level, and, in the event of a low impulse in the deformation direction, the protrusions of the first layer strike against the protrusions of the second layer, and therefore further deformation of the deformation structure in the deformation direction takes place at a relatively high force level.
By this means, it is possible to provide a deformation structure which is deformable at different energy levels depending on a load situation, i.e. a collision impulse, and therefore has different stiffnesses. The “switching over” between the two stiffnesses takes place automatically here independently of a sensor system or an actuator. The setting of the stiffnesses is brought about here by a certain geometrically complementary configuration of the first layer and of the second layer and the connection of the layers via the connecting elements.
According to a development, the first layer and the second layer are furthermore shiftable in a direction parallel to each other by deformation of the web elements.
In particular, the web elements in the case of the deformation structure can be designed in such a manner that they fail in a brittle and/or plastic manner in the event of the high collision impulse, and wherein the web elements act in a manner corresponding to a film hinge in the event of the low collision impulse.
The web elements designed as film hinges can bring about a pivoting movement here of the first layer and of the second layer with respect to each other, in which the first layer and the second layer are shifted parallel to each other and also in the deformation direction, i.e. toward each other.
By this means, a defined pivoting movement of the first layer and of the second layer toward each other is possible, and the stiffness-increasing position of the first layer and of the second layer with respect to each other can be reliably taken up.
In the event of the high collision impulse, the failure of the web elements prevents the pivoting movement of the first layer and of the second layer with respect to each other. On account of the failure of the web elements, the first layer and the second layer are displaced toward each other only in the deformation direction substantially without a lateral yielding movement.
According to a preferred development, the web elements are designed as wall elements or surface elements which extend in the width direction of the first layer and of the second layer. In particular, the web elements can extend here over an entire width of the deformation structure.
In the case of the deformation structure according to the invention, the first layer and the second layer are preferably of substantially identical design or shape.
This facilitates production of the deformation structure. Furthermore, complementary protrusions and depressions are thereby possible in a simple manner.
According to a preferred development of the deformation structure, the protrusions of the first layer and the depressions of the second layer and also the depressions of the first layer and the protrusions of the second layer are arranged lying opposite one another in an initial position of the deformation structure.
By this means, the deformation structure can be deformed in the deformation direction at a relatively low force level in the event of a low collision impulse.
The deformation structure can preferably be formed from a plastics material.
By this means, the deformation structure can be designed to be light and corrosion-resistant.
The deformation structure can preferably be formed integrally here.
This simplifies production and a number of components is thereby particularly small.
The production of the deformation structure from plastic, in particular the integral deformation structure, can take place, for example, by means of extrusion or by an additive production method.
By this means, the deformation structure can be produced particularly efficiently at low cost.
According to a particularly preferred development, the first layer and the second layer are each designed in the form of a corrugated plate. Corrugation crests and corrugation troughs form the protrusions and depressions here.
The protrusions and depressions (corrugation crests and corrugation troughs) can preferably have a trapezoidal configuration.
By means of this geometrical configuration, the protrusions and depressions of the opposite layers are easily displaceable into one another.
The deformation structure according to the present invention can have a multiplicity of layers, wherein two adjacent layers each form a first layer and a second layer. For example, the deformation structure can have three, four, five, six or more layers.
According to a preferred development of the deformation structure, the connecting webs are arranged in a layer intermediate space between two adjacent layers, and the connecting webs of two adjacent layer intermediate spaces are oriented in opposite directions in respect of their shifting action. Shifting action means here, for example, a pivoting movement in opposite directions.
Uniform deformation of the deformation structure with the multiplicity of layers is intended to thereby be achieved in the event of the low collision impulse.
The present invention also relates to a pedestrian protection device for a motor vehicle having a deformation structure according to the invention. The deformation structure is preferably arranged here between a vehicle outer skin element and a body carrier element.
In the event of a collision impulse, the deformation structure is supported here on the body carrier element.
The vehicle outer skin element can be a bumper cladding. The body carrier element can be a bumper cross member.
By means of the pedestrian protection device according to the invention having the deformation structure, a collision sensor system and an actuator system are not necessary for optionally actively locking or unlocking a mechanical mechanism and therefore for being able to switch over as required between a structure with a “soft” deformation behavior and a “stiff” deformation behavior. The pedestrian protection device according to the invention having the deformation structure acts automatically depending on a collision impulse which, in turn, depends on a collision speed of the motor vehicle. The deformation direction is in particular a collision direction and, when used for pedestrian protection in the motor vehicle front, is substantially a longitudinal direction of the vehicle.
In principle, the scope of protection of the deformation structure according to the invention extends, however, also to all other use regions in the automotive sector or else in other technological fields in which deformability of a deformation structure with different load levels depending on a load situation is required.
Accordingly, in the event of the low collision impulse and therefore the low collision speed of the motor vehicle, the opposite layers pivot in such a manner that the protrusions of the opposite layers lie opposite one another and are supported on one another. The deformation structure accordingly acts in a stiff manner. In the event of the high collision impulse and therefore the high collision speed, the opposite layers do not pivot, and therefore the opposite protrusions and depressions of the opposite layer are displaceable into one another. The deformation structure therefore reacts more softly for a longer deformation distance.
For example, the pedestrian protection device can be designed in such a manner that, in the event of a collision impulse which is produced up to a threshold value speed of the motor vehicle, the deformation structure reacts more stiffly, and is deformed in the event of a higher force. At the low collision speed, a collision load can therefore be transferred to the body element located therebehind—at a very low speed—or, in order to protect components located therebehind, energy is sufficiently absorbed by the deformation structure—at a somewhat higher speed which is, however, below the threshold value speed. In each case, the repair costs can therefore be reduced, wherein, in particular at the very low speed—for example in the event of what are referred to as parking prangs or dings—the repair costs can be possibly limited to repairing paint damage, for example.
The threshold value speed can be, for example, 20 km/h or the like.
Furthermore, the pedestrian protection device can be designed in such a manner that, in the event of a collision impulse which is produced from and including the threshold value speed of the motor vehicle, the deformation structure reacts more softly and is deformed with a lower force. This is particularly advantageous in the case of a head-on collision of the pedestrian with the motor vehicle from the threshold value speed since lower collision forces act here on the pedestrian.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.